Biophysical Society Conference | Estes Park 2023

Membrane Budding and Fusion

Poster Abstracts

6-POS Board 2 DEFINING THE ROLE OF SYNAPTOTAGMIN-7 IN INSULIN RELEASE FROM PANCREATIC BETA CELLS. Breanna Coffman 1 ; Maroof Alam 2 ; Peter Arvan 2 ; Arun Anantharam 1 ; 1 University of Toledo, Neurosciences and Neurological Disorders, Toledo, OH, USA 2 University of Michigan, Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine, Ann Arbor, MI, USA Less than five percent of pancreatic tissue is endocrine in nature. Yet, the pancreas serves a vital role in regulating the body’s insulin release in response to elevated glucose levels. The Islets of Langerhans constitute the endocrine component of the pancreas, with much of the tissue being comprised of insulin-secreting beta cells. Here, insulin is synthesized and stored until exocytosis is triggered by elevations in intracellular calcium. Although calcium is known to play a key role in insulin secretion, the specific roles of the calcium sensors that facilitate this process remain unclear. Based on qPCR of FACS-sorted beta cells, we have found that Synaptotagmins (Syts) -7 and -9 are the most highly expressed calcium-sensing Syts, making them prime candidates to be involved in this process. In this study, we focus on Syt7, a high-affinity calcium sensor, whose involvement in calcium-mediated secretion has been demonstrated in multiple cell types. Our experiments utilize a beta cell (Ins1)-specific Syt7 knockout (KO) mouse model that was generated using the Cre/Lox system. Metabolic phenotyping of the beta cell-Syt7 KO male mice maintained on a high- fat diet revealed insulin secretion impairments at times ≥ 60 minutes – a result that is consistent with a deficit in second phase insulin secretion. A particularly powerful feature of our Syt7 KO model is that the beta cells also endogenously express a human insulin tagged with the superfolder green fluorescent protein. With this, TIRF microscopy can be employed to evaluate the secretory consequences of Syt7 gene disruption, ex vivo. The secretory phenotype of the Syt7 KO beta cells, in vivo, and in cell culture, are presented here.

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